1. Field of the Invention
The present invention relates to a sandbag utilising water swelling and absorptive resin.
2. Description of the Related Art
There have been serious flood disasters, both to human and economy, which occurred because of collapse of embankment due to deluge, inundation of houses due to heavy rain, striking of seawater to the land due to the seismic sea wave, sudden and accidental extrusion of water during tunneling work, intrusion of water from entrance to underground facilities due to flood, etc. When the flood disaster occurs, in order to present such a disaster, as temporary and emergency measures for preventing intrusion of water or mud (sand), there has been used a mass of sandbags. A sandbag usually comprises a permeable bag filled with sands, and the sandbags will be cast to the point water will overflow among as area where the water will intrude. However, since large-sued machines cannot be used when such a disaster or accident occurs, the filling of sands should essentially be relied on working by human power, which is of course severe and dangerous, and therefore it is hard to say, because of its poor workability, that the disaster can be prevented completely by using the sandbags as above discussed.
Recently, instead of the above discussed sandbag filled with sands, there has bean provided a sandbag with facile handling and storage, comprising a permeable bag in which water selling and absorptive resin is filled so that, by supplying water therewith or being soaked in water, the sandbag will be gelated and swelled, thus can be used. For example, Japanese Unexamined Patent Publication No. Sho 61-169509 discloses a sandbag filled with powder of the water swelling and absorptive resin. Further, Japanese Unexamined Patent Publication No. Sho 62-133204 discloses a sandbag filled with pellets comprising mixture of water swelling and absorptive resin and fibrous material. However, in regard to each of the above sandbags, the water swelling and absorptive resin of which volume is smaller than the capacity of bag should be filled in the bag in a scattered form (that is, not in a form of lump or single package), thus the filling work thereof in the bag is troublesome, inefficient and not cost-effective. Further, in order to prevent the contents of bag from leaking out of the bag during being swelled, the smaller mesh should be used for the bag. Consequently, the water absorption speed into the bag during water supply would become slower, which results is problematic slower gelation speed of the contents of bag.
On the other head, according to Japanese Unexamined Patent Publication No. Hei 08-134865, there is provided a sandbag comprising water swelling and absorptive resin spread and sandwiched at substantially uniform thickness between two water absorptive sheets which are one size smaller than the bag. The two sheets sandwiching the water swelling and absorptive resin are needle punched and thus fixed, then are inserted in the bag. Since the water swelling and absorptive resin sandwiched between the two or more water absorptive sheets is spread at substantially uniform thickness, part of the water swelling and absorptive resin will not be concentrated at any position in the bag. Accordingly the water absorptive sheet should have certain extent at hardness, thus rather harder fabric such as felt is used for the water absorptive sheet. However, the fabric such as felt ordinarily has poor water absorptivity, thus it has been difficult to accelerate the gelation speed during water supply. In addition, since the water swelling and absorptive resin should be spread and sandwiched at substantially uniform thickness between the two water absorptive sheets, the troublesome working therefor should be required. Further, since the size of sheets sandwiching the water swelling and absorptive resin are only a little smaller than that of the bag (that is, the sizes of the sheets and bag are substantially the same with each other), it requires still troublesome and ineffective working to insert these sheets in the bag. Consequently, as the preparation work is troublesome and ineffective, and as the expensive material such as felt should be need for the water absorptive sheet in order to secure a certain extent of hardness of the sheet, higher cost should be required for manufacturing this kind of sandbag.
In the light of problems which have been described as above, the object of the present invention is to provide a sandbag utilizing water swelling and absorptive resin, with faster water absorption speed, no leakage of contents during being swelled, facile handling, and cost-effectiveness.
For the object as above discussed, according to the present invention, there is provided a sandbag comprising: as outer bag coarsely woven by strong fiber; and a thin inner bag having high permeability, in which the inner bag contains a water soluble peak containing water swelling and absorptive resin.
The sandbag comprises double-layer-bag structure, that is, the outer bag made of textile coarsely woven by strong fiber so that sufficient strength to endure the load of pile of the sandbags may be obtained after being stalled by water, and the inner bag thinner than the outer bag with having high permeability. Since the outer bag has the coarse mesh, and since the inner bag is thin, the fast water absorption can be accomplished. Consequently, since both the outer and inner begs have good permeability, when the sandbag is supplied with water or soaked in water for using thereof, the water will immediately enter inside the bag. In addition, since the water soluble pack will dissolve immediately after being is touch with water, the water entered inside the inner bag will instantly become in touch with the water, swelling and absorptive resin inside the pack, thereby the resin will instantly absorb the water and will be swelled. Thus the gelation speed during water absorption can remarkably be accelerated.
With this structure, since the water swelling and absorptive resin contained in the water soluble pack will absorb pure water of which volume is several tens to hundreds times of that of the resin, and will be swelled end gelated, when the sandbag is supplied with water, or soaked in water, the swelled sandbag can be obtained easily. Further, because of the double-layer-bag structure of the sandbag, although the strong but coarse textile is used for the outer bag, since the smaller mesh is used for the inner bag, the swelled resin can be prevented from leaking out of the bag.
Further, because of the water swelling and absorptive resin contained in the water soluble pack, during manufacturing of the sandbag, that is, when the water soluble pack is enclosed in the sandbag, considerably facile handling of the water swelling and absorptive resin can be accomplished which may result in good workability and cost-effective for manufacturing of the sandbags. In other words, since the water soluble peak will dissolve immediately after being in touch with water, and each a pack will not be any obstacle to swelling of resin, the pack can be minimized, thus the pack can be enclosed in the sandbag easily, with good workability.
For example, the water swelling end absorptive resin can arbitrarily be selected among the group of polyacrylate, polyacrylonitrile saponide (i.e. saponified product thereof), acrylate/vinylalcohol copolymer, starch/acrylic acid graft copolymer, starch/acrylonitrile graft copolymer saponide, cellulose/acrylic acid graft copolymer, polyacrylamide and partial hydrolysate thereof, polyvinyl alcohol, polyethylene oxide, etc.
Preferably, there may be provided a sandbag according to the present invention wherein the outer bag is made of hemp; the inner bag is made of cotton; and the water soluble pack is made of polyvinyl alcohol film, in which the water soluble pack made of polyvinyl alcohol film is prepared by first containing the water swelling and absorptive resin therein and by then being sealed by heat.
The outer bag made of hemp has sufficient strength against the load of pile during used as the sandbag, and if the coarse mesh is adopted thereto, the water absorption map become faster. Further, because of the double-layer-bag structure of the sandbag comprising the outer and inner bags, although the outer bag is made of hemp having coarse mesh, since the inner bag made of cotton has smaller mesh, the water swelling and absorptive resin will absorb water and will be gelated without leaking out of the bag. Further, since the inner bag made of cotton is thin and has excellent permeability, even the double-layer-bag structure of the sandbag will not spoil the water absorptivity of the water swelling and absorptive resin. As the natural fibers such as hemp and cotton are made for the material of the sandbag, when the sandbag should be disposed, any toxic substance such as dioxin will not be generated while being burnt, and there is no bad effect to soil in the case of being buried in the ground.
The polyvinyl alcohol (hereinafter xe2x80x9cPVAxe2x80x9d) ) film used for the water soluble pack will not generate any toxic gas such as chlorine gas during being burnt. Further, there exists microbe which decomposes PVA solved in water. Therefore the PVA film serves as the water soluble plastic film having good characteristic in regard to securing of the environmental and human safety. Further, since various heat sealing machines can easily heat and seal the PVA film, facile manufacturing of the water soluble peak can be accomplished. Since the water swelling and absorptive resin is contained is the thus discussed water soluble pack, the handling thereof is easy, and the water swelling and absorptive resin can be enclosed in the water soluble pack easily. Thus the affective and low-cost manufacture of the sandbags can be accomplished.